Electron tube structure



June 15, 1954 J. w. sKEHAN ELECTRON TUBE STRUCTURE Filed Nov. 1, 1951` mm umm Patented June 15, 1954 ELECTRON TUBE STRUCTURE Joseph W. Skehan, Stamford, Conn., assgnor to Machlett Laboratories, Incorporated, Springdale, Conn., a corporation of Connecticut Application November 1, 1951, Serial No. 254,330

1 Claim. `(Cl. 313-285) This invention relates to a novel electron tube structure. More particularly this invention relates to an electrode support structure having a terminal in the wall of the Vacuum envelope. It also concerns a grid construction of great simplicity.

For years a serious problem in the electronics industry has been the alignment and positioning of elements within electron tubes. The problem involves mechanically supporting the weight of the various electrodes and electrically connecting each electrode to a terminal member having a contact surface outside the tube envelope. Frequently the mechanical support structure has beenfcomplicated, and positioning and alignment of a particular tube element has involved adjustment of a great many members in this support structure. Even after diiiicult and time consuming alignment procedures, the alignment and positioning of the electrodes Within the tube :.f

have often been far from accurate.

My invention provides a solution to the positioning and alignment problem. It employs an extremely simple support member, namely an elongated member of substantially large cross f section, to support the weight of the tube element involved. One end of this elongated support member is aixed to the electrode. The other end of the support member is terminated in a portion of enlarged diameter. portion is received `within a cup-like member which is sealed to the vacuum envelope. The lit between the enlarged portion and the cup is advantageously snug, the cup-like member acting like a socket. The advantage of this n structure lies in the mechanical support provided for the tube element even during adjustment in its position. Using such a structure, the element may be moved in at least one direction and thus positioned as desired before permanently aihxing the enlarged portion within the cup. Once in position, the exact location of the supported element may be permanently preserved by spot welding the enlarged portion of the elongated member to the cup. Such an operation easily and quickly accomplished without moving the tube in any way. Thereafter, particularly if the intended use of the tube calls for rough handling, an even stronger bond may be achieved by the additional use of brazing solder.

Even greater flexibility for positioning and alignment may be acquired by rounding the enlarged portion to an elipsoidal shape. With such a structure the elipsoidal portion acts as The enlarged a ball and the cup-like member acts like a socket, the two together forming a type of ball and socket joint. The elipsoidal portion is therefore usually made almost spherical for best results. Using such a structure, the element to be positioned and aligned may be moved in any direction with ease, and it will be supported in the selected position until finally fixed in place.

In addition to permitting flexibility in element positioning, this type of support structure has a number of other advantages. For instance, the seal between the cup and a vitreous envelope may be made exceptionally strong. The large diameter of such a seal is much more acceptable for supporting the weight of an element than a conventional small diameter wire-glass seal. The joint between the cup-like member and the enlarged portion of the support member forms a heat now path of large cross-section for efficient conductive cooling of the supported element. Similarly, the large cross-section gives an excellent electrical path to the element. The relatively large diameter and the simplicity of the support provide a low inductance path from the terminal to the element. The simplicity of the structure, furthermore, eliminates capacitive eiects which, in the past, have arisen from unduly close spacings between element supports. In general, such a support is strong, strain free, and extremely light.

My support may be used to advantage with any tube element within the vacuum envelope. It is especially valuable for use with a grid structure because positioning oi this electrode is particularly diflicult. It is advantageous, of course, to minimize the weight which must be carried by such support because heavy tube elements necessitate the use of supports of inconveniently large cross-section and, also, because heavy element complicate the type of joint used between them and their supports.

Accordingly, I have invented a light weight grid structure which is especially valuable for use in conjunction with the above described support structure but which has many advantages when employed in other applications. This grid consists of a plurality of parallel wires arranged in a circle and having convergent portions at one end, secured together at this end, and a ring at the other end, to which ring each Wire is ailixed. The support may be conveniently afiixed to this ring. It will be noted that the ring may be made of light material and that no end structure, other than the wires themselves, is employed at the opposite end of the grid. It

flow all the way around the grid. Moreover, it

eliminates the time consuming of welding together the cross wires. Thistwelding, in ad'- dition to requiring the time of a highly skilled welder, may produce embrittlement of the structure adjacent the welds and hot spots at points where welds are poor. Aixing a spiral at numerous points to the grid wires has, also,

caused the introduction` of strains into prior art e grid structures.

For a better understanding of my invention reference is made to the following drawings:

Fig. l shows in cross section an electron tube which employs my invention.

Fig. 2 is a perspective View of the grid and support structure shown in Fig. l.

In a preferred embodiment, my invention employs a glass, globe-like envelope ifi* which has a narrow neck i i at one end and an enlarged neck l2 at the other end which accommodates a reentrant envelope portion 12a. The reentrant end portion ld is terminated in stern press I3 through which passes rod-like conductors It and I5. The rod-like conductor it extends into the globe-lilteportion of the envelope ES and is affixed byY welding or other suitable means to the near-pressenti of spiral filament l. The oppcsite end of filament l5 is similarly affixed to rodlike member il which lies on the tubes axis and is advantageousiy terminated within and supported by the stem press i3. The rod-like members Ul and il serve the dual function of filament leads within the vacuum envelope and nlament support members. A cup-like heat shield 22 is provided to protect the stem press. Outside of the vacuum envelope; the conductors It and iii are terminated in flexible filament leads i9 and 2li respectively. An exhaust tubulation 23 is advantageously ported into the vacuum envelope through the stein press i3 so that the tubulation 2t is protected by its location within the reentrant envelope portion ld.

The grid structure of Fig; 1 is shown in greater detail in The grid consists of a plurality of parallel wires or strands 2d having convergent portions near one end. These convergent portions are secured together at this end in some convenient fashion, as by binding them with wire 25 and welding them in place. At the opposite end of the grid structure each of the wires is individually ailixed to a ring 23. The ring. is'in turn aiixed by welding, bracing, or other convenient means to an elongated relatively rigid support member 2l. In this case this support member is tubular and has one end flattened and bent out of` the axial line in such a way as'to aford a convenient surface for alixing it to the grid ringV 2t. The end of the support member opposite that attached to the grid structure is terminated in a portion 28 of elipsoidal, spheroidal, or spherical shape. The lip 29a of the cup 29, which is composed of a glass-sealing metal like Kovar, is affixed to a neck lea in the side wall of the vacuum envelope in a position cond il versal adjustment of the position of the supported element. For instance, adjustment of the electrode position along the axis of the support member 2'! is accommodated by modifying the depth ofl penetration of the ball-like portion 23 within cup 29. All other position adjustment is accomplished by rotation of the ball-lil e portion 2t within-cup 29. Once in the desired position, inadvertent change in position may be prevented by spot-welding the elipsoidal portion 28 to cup 2e'. Thereafter, a solid, more conductive joint may be made by bracing together the two members.

As shown inv Fig. l, a tubular extension 3811s axed to ring 2tv of the grid structure. A ring 3l of somewhatsmaller diameter is affixed to the lament structure (here conductor I4) coaxial "ith ring 3e. These two rings are employed to add capacitance between grid and cathode elements when tube specifications call for more capacitance than the small amount afforded by the oppcsing surfaces of elements and supports using my greatly simplified type construction. By increasing the amount of surface mutually opposed, the capacitance may be further increased.

At the end ci the vacuum enveiope opposite the stem press lovar cup member 33 is sealed to neck il of the vacuum envelope. Cup 33 is advantageously made with a reduced diameter portion 33a which snugly accommodates an enlarged portion 3ft of elongated anode support 35. The anode 35 is a tubular member preferably with a cap 3l at its supported end. The anodeA is ad- Y vantageously supported at three points by wire like support members 33. Thesev wire-like supports t8 have parallel portions which are advantageously afxed to the anode capY by doubling baci: on themselves aroundl the edge of the cap. Convergent portions of tre wire-like members 38 are terminated in parallel axial portions which advantageously-fit and are sealed in an ax-ial hole 35a in the end of member 3d. t may be noted that the enlarged portion 3d of the support 35 in this instance is approximately cylindrical. By exercising great care in sealing cup 35% toY neck li the axial alignment of the cup may be preserved. Then, if member 3ftv is made perfectly cylindrical and concentric with the support member 35 a snug rit between members S4 and 33 will assure accurate alignment oi anode 3% while permitting adjustment of its axial level. li more flexibility in adjustment and positioning of the Y anode is desired, the enlarged portion 3A' may be made elipsoidal or ball-lile similar to the corresponding portion 2G of the grid support.

In assembling the tube structure as shown the anode member is advantageously rst introduced. Because of accurate'alignment or" the cup relative to the envelopey iii and the enlarged portion relative to the support, the anode is automatically aligned upon the axis of the tube and needs only to be positioned at the correct axial level and fixed in place. The structure shown in Fig. 2 may then be introduced into the envelope and the grid cage located within the anode structure while the spherical portion .t5 of support 3l!` is positioned within cupii.k If the tube structure is placed in a glass lathe, or upon some sort of centering fixture, a centering mandrel tool placed within the grid structure will insure its axial alignment and proper positioning relative to the anode. When the proper position for the grid has been found the enlarged portion 35 may be secured to the cup by spot Welding Without removing the tube from the glass lathe or the iixture. Thereafter, the lament-stem press structure may be placed Within the chuck of the glass lathe opposing the envelope and advanced so that the lament is properly introduced Within the grid structure. With the lament correctly in place, the vacuum envelope is completed by sealing the portion supporting the filament to the main body of the envelope. The reentrant portion of the envelope 12a, as Well as stem press I3 support the filament so that the final seal between neck I2 and reentrant portion ma may be conveniently made at the tubes end. Thus sealed in position, permanent accurate alignment of the filament relative to other electrodes is assured.

I claim:

An electron tube containing an electrode, the support member for said electrode comprising a relatively rigid elongated member one end of whieh is affixed to said electrode and the other end of which is terminated in an elipsoidal portion and a, metal cup-like member sealed to the vacuum envelope in position to receive the elipsoidai portion so that the supported electrode may be subjected to universal movement in determining its proper position.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,217,418 Rabuteau. Oct. 8, 1940 2,277,148 Ronci Mar. 24, 1942 2,376,288 Sphar May l5, 1945 20 2,516,841 Arditi et al Aug. 1, 1950 

